Diode-pumped solid-state laser having a thermal lens inside the resonator

Abstract

Disclosed is a diode-pumped solid-state laser having an asymmetrical optical resonator provided with at least two resonator mirrors, inside said resonator being provided at least one thermal lens having an optical refractive power D and having two principal planes respectively and said resonator being definable by the following stability criteria: 0<G 1 ·G 2 <1 with G 1=1 −L*/R 1 −D·d 2 G 2=1 −L*/R 2 ·D·d 1 and L*=d 1 +d 2 −D·d 1 ·d 2 d 1 ,d 2 the distances of the resonator mirror from the principal planes of the thermal lens R 1 , R 2 the radii of curvature of the resonator mirrors. The invention is distinguished by the values d 1 ,d 2 ,R 1 and R 2 being selected in such a manner that the following critical refractive powers D I ,D II ,D III and D IV , for which D I = - 1 R 1 - d 1 - 1 R 2 - d 2 , D II = 1 d 2 - 1 R 1 - d 1 , D III = 1 d 1 - 1 R 2 - d 2 , D IV = 1 d 1 + 1 d 2 applies, the following equations are fulfilled: D II −D I =D IV −D III ≧8 dptr. | D III −D II |≧2 dptr.

1. A diode-pumped solid-state laser having an asymmetrical optical resonator provided with at least two resonator mirrors, inside said resonator being provided at least one thermal lens having an optical refractive power D and having two principal planes respectively and said resonator being definable by the following stability criteria:
   0 <G   1   ·G   2 <1 
   with 
     G   1 =1 −L*/R   1   −D·d   2    
     G   2 =1 −L*/R   2   ·D·d   1    
   and 
     L*=d   1   +d   2 −D·d 1   ·d   2    
 d 1 ,d 2  the distances of the resonator mirror from the principal planes of the thermal lens 
 R 1 ,R 2  the radii of curvature of the resonator mirrors 
 
     wherein the values d 1 , d 2 , R 1  and R 2  are selected in such a manner that the following critical refractive powers D I ,D II ,D III  and D IV , for which 
     
       
         
           
             
               
                 
                   
                     
                       D 
                       I 
                     
                     = 
                     
                       
                         - 
                         
                           1 
                           
                             
                               R 
                               1 
                             
                             - 
                             
                               d 
                               1 
                             
                           
                         
                       
                       - 
                       
                         1 
                         
                           
                             R 
                             2 
                           
                           - 
                           
                             d 
                             2 
                           
                         
                       
                     
                   
                   , 
                 
               
               
                 
                   
                     
                       D 
                       II 
                     
                     = 
                     
                       
                         1 
                         
                           d 
                           2 
                         
                       
                       - 
                       
                         1 
                         
                           
                             R 
                             1 
                           
                           - 
                           
                             d 
                             1 
                           
                         
                       
                     
                   
                   , 
                 
               
             
           
         
       
       
         
           
             
               
                 
                   
                     
                       D 
                       III 
                     
                     = 
                     
                       
                         1 
                         
                           d 
                           1 
                         
                       
                       - 
                       
                         1 
                         
                           
                             R 
                             2 
                           
                           - 
                           
                             d 
                             2 
                           
                         
                       
                     
                   
                   , 
                 
               
               
                 
                   
                     D 
                     IV 
                   
                   = 
                   
                     
                       1 
                       
                         d 
                         1 
                       
                     
                     + 
                     
                       1 
                       
                         d 
                         2 
                       
                     
                   
                 
               
             
           
         
       
     
     applies, the following equations are fulfilled:
     D   II   −D   I   =D   IV   −D   III ≧8dptr. 
   | D   III   −D   II |≧2dptr. 
 
   
   
     2. The diode-pumped solid-state laser according to  claim 1 , wherein an intracavity quality-switch or an extracavity modulator is provided. 
   
   
     3. The diode-pumped solid-state laser according to  claim 2 , wherein said quality-switch is an intracavity acouso-optical or electro-optical Q-switch. 
   
   
     4. The diode-pumped solid-state laser according to  claim 1 , wherein said asymmetrical optical resonator is provided with a convex-plane, convex-concave or convex-convex resonator construction. 
   
   
     5. The diode-pumped solid-state laser according to  claim 1 , wherein provided is an intracavity laser medium in the form of at least one laser crystal doped with one or a multiplicity of the following doping substances: Nd, Yb, Cr, Tm, Ho or Er. 
   
   
     6. The diode-pumped solid-state laser according to  claim 5 , wherein said laser crystal comprises the following doped crystals: Nd:YAG, Nd:YVO 4 , Nd:YLF, Nd:GVO 4 , Nd:YPO 4 , Nd:BEL, Nd:YALO, Nd:LSB, Yb:YAG, Yb:FAB, Cr:LiSAF, Cr:LiCAF, Cr:LiSGAF, Cr:YAG, Tm—Ho:YAG, Tm—Ho:YLF, Er:YLF or Er:GSGG. 
   
   
     7. The diode-pumped solid-state laser according to  claim 5 , wherein said laser crystal possesses strong thermal optical focussing properties and represents said thermal lens inside said resonator. 
   
   
     8. The diode-pumped solid-state laser according to  claim 1 , wherein at least one diode laser unit is provided as said pumped-light source, whose pumped light is directed or deflected in longitudinal direction to the optical axis of said thermal lens. 
   
   
     9. The diode-pumped solid-state laser according to  claim 1 , wherein using a Nd:YVO 4  laser crystal and pumped-light power of at least 10 W, the following peak pulse powers PP are attainable based on the pulse repetition frequency RF, at which the solid-state laser is operatable: 
     
       
         
               
               
               
             
                   
                   
               
                   
                 RF[kHz] 
                 PP[kW] 
               
                   
                   
               
                   
               
               
               
               
             
                   
                 10 
                 >60 
               
                   
                 30 
                 >30 
               
                   
                 60 
                 >10 
               
                   
                 90 
                 >5. 
               
                   
                   
               
           
              
              
              
             
             
              
             
          
           
              
              
              
              
              
             
          
         
       
     
   
   
     10. The diode-pumped solid-state laser according to  claim 9 , wherein the laser pulses emitted by said solid-state laser have the following pulse widths PW at pulse repetition frequencies RF: 
     
       
         
               
               
               
             
                   
                   
               
                   
                 RF[kHz] 
                 PW[ns] 
               
                   
                   
               
                   
               
               
               
               
             
                   
                 10 
                 ~7 
               
                   
                 20 
                 ~10 
               
                   
                 30 
                 ~14 
               
                   
                 50 
                 ~18 
               
                   
                 75 
                 ~22 
               
                   
                 100  
                 ~28 
               
                   
                 150  
                 ~35.